The Federal Communications Commission (FCC) has authorized ultra-wide-band (UWB) communication between 3.1 GHz and 10.6 GHz. Since UWB pulses rely on ultra-short (nanosecond scale) waveforms to have UWB spectral occupancy, UWB radios come with unique advantages: i) enhanced capability to penetrate through obstacles; ii) ultra high precision ranging at the centimeter level; iii) potential for very high data rates along with high user capacity; and iv) smaller circuit sizes with less power consumption.
On the other hand, these ultra-short UWB signals bring some drawbacks. For many receiver architectures, a large percentage of the power dissipation is associated with the estimation of the timing offset of UWB signals. This estimation of the timing offset is the so-called acquisition. For the acquisition, a scan of all clock phases in the full UWB pulse frame is done by means of a delay line in order to find a timing position in the pulse frame such that this timing position has sufficient correlation energy for a known trail of pulses. The acquisition delay line requires a high degree of accuracy (typically ½ of the pulse duration, 1 ns) and coverage of the full frame duration that can range from 10 ns to 300 ns. So far there is no solution for a low-power delay line that features an update of the delay in a single or only a few clock cycles over a wide range/wide-spread of delay values.
More in general, delay lines have been described for example in Hsiang-Hui Chang et al., “A Wide-Range Delay-Locked Loop With a Fixed Latency of One Clock Cycle”, IEEE Journal Of Solid-State Circuits, Vol. 37, No. 8, August 2002, and in Yi-Ming Wang et al., “A Low-Power Half-Delay-Line Fast Skew-Compensation Circuit”, IEEE Journal Of Solid-State Circuits, Vol. 39, No. 6, June 2004. In the latter document, a delay line is described composed of a plurality of delay units, arranged in series, and a tracking mechanism for tracking the propagation of the clock signal through the delay line. The tracking mechanism measures at the input of each of the delay units and is therefore highly power consuming.